Reducing rolling resistance of pneumatic tires is demanded for enhancing fuel economy performance of vehicles.
At the same time, providing excellent wet grip performance is essential to a pneumatic tire.
In general, silica is blended in rubber compositions for tires to improve low rolling resistance and wet grip performance.
It is empirically known that the wet grip performance of a rubber composition can be improved by increasing the blended amount of silica.
However, when the amount of silica is increased, there is generally the problem that the dispersibility of the silica deteriorates and rolling resistance ends up increasing.
That is, it is difficult to improve both low rolling resistance and wet grip performance with a rubber composition containing a large blended amount of silica.
International Patent Application Publication No. WO/2014/002750 proposes blending certain silane coupling agents containing a mercapto group to improve the dispersibility of silica.
However, when the blended amount of silica was high, silica dispersibility was not necessarily sufficiently improved even when such a silane coupling agent was blended. Thus, achieving both low rolling resistance and wet grip performance at a higher level has still been demanded.